The present invention relates to nonvolatile erasable programmable memories and more specifically, techniques for erasing, programming, or reading these types of memories.
Memory and storage is one of the key technology areas that is enabling the growth in the information age. With the rapid growth in the Internet, World Wide Web (WWW), wireless phones, personal digital assistant, digital cameras, digital camcorders, digital music players, computers, networks, and more, there is continually a need for better memory and storage technology. A particular type of memory is nonvolatile memory. A nonvolatile memory retains its memory or stored state even when power is removed. Some types of nonvolatile erasable programmable memories include Flash, EEPROM, EPROM, MRAM, FRAM, ferroelectric, and magnetic memories. Some nonvolatile storage products include CompactFlash (CF) cards, MultiMedia cards (MMC), Flash PC cards (e.g., ATA Flash cards), SmartMedia cards, and memory sticks.
A widely used type of semiconductor memory storage cell is the floating gate memory cell. Some types of floating gate memory cells include Flash, EEPROM, and EPROM. The memory cells are configured or programmed to a desired configured state. In particular, electric charge is placed on or removed from the floating gate of a Flash memory cell to put the memory into two or more stored states. One state is an erased state and there may be one or more programmed states. Alternatively, depending on the technology and terminology, there may be a programmed state and one or more erased states. A Flash memory cell can be used to represent at least two binary states, a 0 or a 1. A Flash memory cell can store more than two binary states, such as a 00, 01, 10, or 11; this cell can store multiple states and may be referred to as a multistate memory cell. The cell may have more than one programmed states. If one state is the erased state (00), the programmed states will be 01, 10, and 11, although the actual encoding of the states may vary.
Despite the success of nonvolatile memories, there also continues to be a need to improve the technology. It is desirable to improve the density, speed, durability, and reliability of these memories. It is also desirable to reduce power consumption.
As can be seen, there is a need for improving the operation of nonvolatile memories. Specifically, by allowing background operation of the nonvolatile memory cells, this will speed up operations and reduce power consumption.